Ocean acidification due to increasing atmospheric carbon dioxide

30 June 2005

Carbon dioxide (CO2) emitted to the atmosphere by human activities is being absorbed by the oceans, making them more acidic (lowering the pH the measure of acidity).

Evidence indicates that emissions of carbon dioxide from human activities over the past 200 years have already led to a reduction in the average pH of surface seawater of 0.1 units and could fall by 0.5 units by the year 2100. This pH is probably lower than has been experienced for hundreds of millennia and, critically, at a rate of change probably 100 times greater than at any time over this period.

The report outlines our best understanding of the impacts of these chemical changes on the oceans. The impacts will be greater for some regions and ecosystems, and will be most severe for coral reefs and the Southern Ocean. The impacts of ocean acidification on other marine organisms and ecosystems are much less certain. We recommend a major international research effort be launched into this relatively new area of research.

We recommend that action needs to be taken now to reduce global emissions of CO2 from human activities to the atmosphere to avoid the risk of irreversible damage from ocean acidification.